As the number of smartphones/tablets with WiFi connection capability keeps growing, the density of access points (APs) and stations (STAs) is getting higher, especially in urban areas. The high density of APs and STAs makes WiFi system less efficient since the original WiFi system was designed assuming a low density of APs and STAs. For example, the current enhanced distributed channel access (EDCA-based) media access control (MAC) scheme will not work efficiently in an environment with a high density of APs and STAs. As a result, a new Study Group (SG) called High Efficiency Wireless Local Area Network (WLAN) (HEW) was formed in IEEE 802.11 to improve system performance in high density environments. As a result of the study of the HEW SG, a Task Group called TGax was formed in May 2014.